How do you MAPped it right with TWM :hmmmm: where you get the reading from ?
MAP sensor tapping?
That's strange, because TWM gives the vacuum accumulator/vacuum log along (unless you bought it without, I dunno lah), so tap from that, you might need a vacuum distribution block for the brakes and fuel regulator and other vac-reference required sensors(map) or meters/auxbox whatever.
You can look up the design from golden eagle and other manufacturers and machine one up, or order if you want the bling bling logo on it.
Toda doesn't, you have the vac ports on the velocity stacks (or was it on the adapter end for the head? I forget), tap them to a vacuum log or something, I remember seeing a ghetto setup where the ITB's vacuum log was a short plastic pipe.. WTF? You buy a few thousand ringgit ITB and you use an el-cheapo plastic pipe for a vacuum log? WTF indeed.....
Go machine shop and machine one also not that expensive I think.. plastic... NUTS!
As with all ITB's using MAP sensors, there is the slight problem of having zero vacuum at part throttle at low rpms, which is usually the case with running super huge throttle bodies on the plenum, or having ITBs (which has huge part throttle openings as well). The slow pistons speeds are not generating enough air speed to generate vacuum at the vacuum log, so your fuelling is jumping from one end to another in the fuel/ignition mapping, and if you set it to compensate, your WOT torque at low rpm is going to be crap.
If you are familiar with MAP based fuel maps, that's the problem because fuelling can never be regulated constantly at low rpm because the MAP sensor isn't getting good vacuum signal, at low pistons speeds (aka low rpm).
There's way of going around that by running high engine idle, FICD, etc. but when you spend that much for ITBs and use VAFC, something must be wrong somewhere.. lol. When you play with alpha-n, all becomes clear how ITBs are supposed to be tune, and that problem with daily drivability, idling, etc goes away.
So you have to tune by TPS percentage(also known as
alpha-n). There's also the option in hondata of running partial TPS mode at low rpm and switching to MAP at high rpm (where the map can read proper vacuum, thanks to higher piston speeds) in Hondata for better fuel economy
(and also compensation for elevation changes/colder hotter air - in theory).
The theory part begins (I never tested this, so it's theory)
In theory, full alpha-n systems don't compensate fuelling like map systems based on pressure and intake temp, so elevation changes don't affect fuelling on alpha-n systems, unlike MAP, so that's why hondata offers it (so does crome, I think).
This is what I understood from what little hondata admins told me (about why we still retain MAP sensor when we run TPS based map/alpha-n.)
For this setup, it's managed by powerFC, and damn, is the two similar.. except for a few missing features, not sure if it's the FCdatalogit or commander unit, or maybe the original japan software has more features not shown in FC datalogit.
Tuning by alpha-n, it's very easy to get it to idle... PowerFC goes one better and does it automatically, once you set the parameters. Might be a good thing or a bad thing, because you need to just leave it for a few minutes while it corrects, (waste time, waste fuel?)
That's one feature I didn't know existed till I played with it.. Auto idle adjustment, just start and leave it, powerFC does the rest. (O_o)
Only did a base tune on one before so it's drivable, not for power though, so didn't play with post vtec rpms.
You might want to run open loop for better idling too, as the compensation on honda ecu's are horribly strict.. they want you to idle/cruise at stoich, and they adjust fuelling to suit. Kind of irritating once you get used to the throttle response when you run open loop. I've run open loop for close to a year now, and never looked back. closed loop is a form of their compensation to fit emission laws. We don't have that yet, so enjoy it while it lasts.. >P
I'm not entirely sure what purpose the MAP sensor has in the powerfc or hondata, but for this setup, it's connected anyway, though fuelling with alpha-n doesn't seem to need it, maybe for compensation factors, in which case, the theory part might be wrong about full alpha-n not having compensation.
Opps... I just checked the hondata prog I have.. the MAP sensor IS for atmospheric compensation.. I guess that's the primary reason for retaining the MAP sensor, but for hondata, you can actually turn it off. I didn't notice it before...
I didn't notice this in FC-datalogit too, though it's probably there.
Or maybe hondata admins meant what they said for MAF sensor engines running ITBs? there's no clear way of having atmospheric compensation for MAF type engine management.
